/**
 * Utility class for manipulating CSS rules
 * @singleton
 */
Ext.define('Ext.util.CSS', function() {
    var rules = null;
    var doc = document;

    var camelRe = /(-[a-z])/gi;
    var camelFn = function(m, a){ return a.charAt(1).toUpperCase(); };

    return {

        singleton: true,

        constructor: function() {
            this.rules = {};
            this.initialized = false;
        },

        /**
         * Creates a stylesheet from a text blob of rules.
         * These rules will be wrapped in a STYLE tag and appended to the HEAD of the document.
         * @param {String} cssText The text containing the css rules
         * @param {String} id An id to add to the stylesheet for later removal
         * @return {CSSStyleSheet}
         */
        createStyleSheet : function(cssText, id) {
            var ss,
                head = doc.getElementsByTagName("head")[0],
                styleEl = doc.createElement("style");

            styleEl.setAttribute("type", "text/css");
            if (id) {
               styleEl.setAttribute("id", id);
            }

            if (Ext.isIE) {
               head.appendChild(styleEl);
               ss = styleEl.styleSheet;
               ss.cssText = cssText;
            } else {
                try{
                    styleEl.appendChild(doc.createTextNode(cssText));
                } catch(e) {
                   styleEl.cssText = cssText;
                }
                head.appendChild(styleEl);
                ss = styleEl.styleSheet ? styleEl.styleSheet : (styleEl.sheet || doc.styleSheets[doc.styleSheets.length-1]);
            }
            this.cacheStyleSheet(ss);
            return ss;
        },

        /**
         * Removes a style or link tag by id
         * @param {String} id The id of the tag
         */
        removeStyleSheet : function(id) {
            var existing = document.getElementById(id);
            if (existing) {
                existing.parentNode.removeChild(existing);
            }
        },

        /**
         * Dynamically swaps an existing stylesheet reference for a new one
         * @param {String} id The id of an existing link tag to remove
         * @param {String} url The href of the new stylesheet to include
         */
        swapStyleSheet : function(id, url) {
            var doc = document;
            this.removeStyleSheet(id);
            var ss = doc.createElement("link");
            ss.setAttribute("rel", "stylesheet");
            ss.setAttribute("type", "text/css");
            ss.setAttribute("id", id);
            ss.setAttribute("href", url);
            doc.getElementsByTagName("head")[0].appendChild(ss);
        },

        /**
         * Refresh the rule cache if you have dynamically added stylesheets
         * @return {Object} An object (hash) of rules indexed by selector
         */
        refreshCache : function() {
            return this.getRules(true);
        },

        // private
        cacheStyleSheet : function(ss) {
            if(!rules){
                rules = {};
            }
            try {// try catch for cross domain access issue
                var ssRules = ss.cssRules || ss.rules,
                    selectorText,
                    i = ssRules.length - 1,
                    j,
                    selectors;

                for (; i >= 0; --i) {
                    selectorText = ssRules[i].selectorText;
                    if (selectorText) {

                        // Split in case there are multiple, comma-delimited selectors
                        selectorText = selectorText.split(',');
                        selectors = selectorText.length;
                        for (j = 0; j < selectors; j++) {
                            rules[Ext.String.trim(selectorText[j]).toLowerCase()] = ssRules[i];
                        }
                    }
                }
            } catch(e) {}
        },

        /**
         * Gets all css rules for the document
         * @param {Boolean} refreshCache true to refresh the internal cache
         * @return {Object} An object (hash) of rules indexed by selector
         */
        getRules : function(refreshCache) {
            if (rules === null || refreshCache) {
                rules = {};
                var ds = doc.styleSheets,
                    i = 0,
                    len = ds.length;

                for (; i < len; i++) {
                    try {
                        if (!ds[i].disabled) {
                            this.cacheStyleSheet(ds[i]);
                        }
                    } catch(e) {}
                }
            }
            return rules;
        },

        /**
         * Gets an an individual CSS rule by selector(s)
         * @param {String/String[]} selector The CSS selector or an array of selectors to try. The first selector that is found is returned.
         * @param {Boolean} refreshCache true to refresh the internal cache if you have recently updated any rules or added styles dynamically
         * @return {CSSStyleRule} The CSS rule or null if one is not found
         */
        getRule: function(selector, refreshCache) {
            var rs = this.getRules(refreshCache);
            if (!Ext.isArray(selector)) {
                return rs[selector.toLowerCase()];
            }
            for (var i = 0; i < selector.length; i++) {
                if (rs[selector[i]]) {
                    return rs[selector[i].toLowerCase()];
                }
            }
            return null;
        },

        /**
         * Updates a rule property
         * @param {String/String[]} selector If it's an array it tries each selector until it finds one. Stops immediately once one is found.
         * @param {String} property The css property
         * @param {String} value The new value for the property
         * @return {Boolean} true If a rule was found and updated
         */
        updateRule : function(selector, property, value){
            if (!Ext.isArray(selector)) {
                var rule = this.getRule(selector);
                if (rule) {
                    rule.style[property.replace(camelRe, camelFn)] = value;
                    return true;
                }
            } else {
                for (var i = 0; i < selector.length; i++) {
                    if (this.updateRule(selector[i], property, value)) {
                        return true;
                    }
                }
            }
            return false;
        }
    };
}());